1. Field of the Invention
The present invention relates to a driverless vehicle system and method which utilizes a fixed and movable camera to monitor the road upon which the driverless vehicle system is travelling.
2. Description of Related Art
Various types of driverless vehicle systems are known in the art. Generally, conventional driverless vehicle systems utilize a fixed camera which takes images of the road upon which the vehicle is travelling. Using image recognition techniques, these conventional driverless vehicle systems identify road boundaries, obstacles, a desired travelling path, and a current vehicle travelling direction. Based on the desired travelling path and the direction in which the vehicle is travelling, the conventional driverless vehicle system calculates a tracing angle which is the angle between the desired travelling path and the vehicle's current travelling path. Based on the tracing angle, the steering angle of the vehicle can be controlled to eliminate the tracing angle.
U.S. Pat. No. 4,819,169 entitled SYSTEM AND METHOD FOR CALCULATING MOVEMENT DIRECTION AND POSITION OF AN UNMANNED VEHICLE to Saitoh et al., hereby incorporated by reference, discloses such a conventional driverless vehicle system. FIG. 3 illustrates the theory behind the driverless vehicle system of Saitoh. As shown in FIG. 3, Saitoh discloses a fixed camera 101 mounted on a vehicle 103. The camera 101 has a field of view defined by field of view boundary lines 109 and 111. The camera 101 is arranged such that the center line 105 of the field of view for the camera 101 coincides with the current travelling path of the vehicle. As disclosed in Saitoh, by using image recognition techniques, the road boundaries 200 and 300 can be determined. Based on the determination of road boundaries 200 and 300, a desired travelling path 107 is determined. The desired travelling path 107 is established by selectively choosing the distances W1 and W2 that the desired travelling path should lie from the road boundaries 200, 300. Having established the desired travelling path 107 and the current travelling path, the tracing angle .theta. is calculated. Based on the tracing angle .theta., steering control is effected to eliminate the tracing angle in any well known manner.
As discussed above, conventional driverless vehicle systems such as disclosed by Saitoh only utilize a single fixed camera. Such driverless vehicle systems are limited to travelling on relatively straight or very gently curving roadways. If the conventional driverless vehicle system is used on a roadway having sharp curves, then the situation arises wherein one of the road boundaries 200, 300 will not lie within the field of view of the camera 101. In other words, because of a sharp curve in the roadway, one of the field of view boundary lines 109 and 111 will not intersect a corresponding one of the road boundaries 200, 300. As a result, the image taken by the camera 101 will not contain sufficient information for proper image recognition.